Ligue 1 Preview: Saint-Etienne v PSG
The defending champions are currently four points off the pace in the league after surprising defeats to Bastia and Guingamp, however they got themselves back on track with a 4-2 win over Evian last time out.
Much more is expected of PSG, though, and they need to drastically improve if they want to reignite their league campaign with Lyon and Marseille both ahead of them in first and second respectively.
Saint-Etienne have exceeded expectations this season and only trail Laurent Blanc's side by one point ahead of Sunday's meeting, and PSG's Blaise Matuidi knows they must perform better to ensure they do not slip out of the top three.
"It will be a very important match," the former Saint-Etienne midfielder told the club's official website.
"Of course, the Stade Geoffroy Guichard is always special for me. But we really need points to stay glued to the leaders. We want to return the top.
"It will be tough, because winning in Saint-Etienne is always complicated. But it is our ambition."
Recent history suggests that the visitors will emerge with all three points after four successive wins over their hosts, including a 1-0 Coupe de la Ligue victory earlier this month.
Saint-Etienne have not beaten their illustrious opponents since November 2012, and have failed to take all three points at home in this fixture in over six years.
And Saint-Etienne boss Christophe Galtier says it would be a big achievement for his side to get anything from the game, especially with a depleted squad.
Galtier has lost Moustapha Bayal Sall and Kevin Monnet-Paquet this week, and with three players on international duty at the Africa Cup of Nations he has a limited number to select from.
"Given the injuries and Africa Cup of Nations call-ups, I prepare for this meeting with 12 outfield players," he said.
"The gap between us and PSG was already there, so it will be even more on Sunday. We have to be imaginative and build on our training.
"We're chasing a big challenge. PSG are much better than us, they are not a direct competitor at all.
"Paris is and will be champions at the end of the season. PSG are the best team in the league and one of the best in Europe."
Much will rest on the form of strikers Mevlut Erdinc and Ricky van Wolfswinkel, who have eight league goals between them this season.
The latter scored twice in their 5-3 Coupe de France win over Tours on Wednesday, but has not scored in Ligue 1 since December 21.